Eastern tent caterpillars
spend the winter as ring-like masses of eggs that were laid last June on
twigs of wild cherry, crabapples, and related trees. It is possible to
check trees for masses now to get some idea on the potential caterpillar
population this spring. If large numbers are easily found, then it is obvious
that managers must be ready to deal with the caterpillars after egg hatch.
If few or no masses are found, it will still be important to watch those
trees for tents in late March and early April

“Spent” egg masses from which
caterpillars emerged last year may be present so it is important to be
able to distinguish between new and old ones. This is not hard and the
pictures below will show you how. A hand magnifying lens and a sharp-tipped
needle will be useful in checking masses that you find. Most all new (and
some old egg masses) should be within 15 to 18 inches of the tip of twigs
that are about one-quarter inch in diameter. There does not seem
to be a height preference so masses can be anywhere up and down the height
of the tree.

New Masses

Individual tent caterpillar
eggs in “live” masses (those laid during the summer of 2002) are white
but the entire mass is covered partly to entirely with a shiny, varnish-like
material called spumaline (Figure 1).

Figure 1

New egg masses will be made
up of eggs with intact white tops (Figure 2). You may want to scratch
some of the spumaline away so that you can see the ends of the eggs to
confirm whether they are new or old.

Figure 2

Old Masses

Many of the masses that hatched
in 2002 have weathered and fallen from the trees but some will still be
present. Old masses will not have much, if any, of the hard covering and
the individual eggs in the mass will have a definite hole in the top (Figure
3). You may find old masses in which a few eggs did not hatch for some
reason. They will not hatch this year.

Figure 3

How to Use the Information.

Tree checks now would allow
you to get some idea if many masses are present or that they are relatively
scarce. If lots of new masses are present, then these are high priority
areas that should be checked for tents as egg hatch progresses in the spring.
There is nothing that can be done at this point to kill egg masses and
caterpillars, short of physically removing them individually. Control measures,
such as tent destruction or removal, sprays, injections, etc., need to
be done after egg hatch in March.

Finding egg masses when numbers
are low, just a few per tree, is like a search for a needle in a haystack.
Lots of time can be spent with no obvious return and small numbers of tents
may be present. General indications from the tree checks made by UK entomology
personnel point to a reduced population for 2003 but numbers can vary greatly
from one location to another.